Washing machine

ABSTRACT

A washing machine which has a structure capable of generating bubbles in wash water. The washing machine includes a main body, a tub vertically arranged within the main body, a passage case including a first drainage pipe connected to a lower portion of the tub and a branch pipe to allow wash water introduced from the first drainage pipe to be introduced into the tub again, a pump including a pump case having a first pump inlet arranged at a relatively higher position than the branch pipe and a motor coupled to one end of the pump case so as to supply power to pump the wash water introduced into the first pump inlet, and a bubble generating unit to generate bubbles in the wash water pumped by the pump.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2010-0133107 filed on Dec. 23, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present disclosure relate to a washing machine having structures to generate bubbles in wash water introduced into a tub and rotary tub of the washing machine, and to outwardly discharge the wash water within the tub and rotary tub of the washing machine.

2. Description of the Related Art

Washing machines are utilized to wash clothes using electric power. Such a washing machine generally includes a tub to store wash water, a rotary tub rotatably installed within the tub, a pulsator rotatably mounted at a base of the rotary tub, and a motor to rotatably drive the rotary tub and the pulsator.

When the rotary tub and the pulsator are rotated by the motor in a state in which laundry and wash water are put into the rotary tub, the pulsator agitates the laundry, which is put into the rotary tub, together with the wash water to remove stains from the laundry.

In the case of a general fully automatic washing machine, powdered washing agents are supplied to a washing tub in an initial stage of a washing course, or liquid washing agents (rinse agents), etc. stored in a washing agent container are automatically put into the washing tub according to washing conditions such as a washing or rinsing course. The washing agents put into the washing tub are then decomposed or dissolved in water by rotation of the pulsator. In this case, it takes considerable time to decompose or dissolve the washing agents. That is, since the fully automatic washing machine decomposes or dissolves the washing agents only by rotational force of the pulsator, there is a limit to improvement of washing efficiencies and washing qualities.

SUMMARY

Therefore, it is an aspect of the present disclosure to provide a washing machine which has a structure capable of generating bubbles in wash water.

It is another aspect of the present disclosure to provide a washing machine which has a structure capable of smoothly discharging wash water to the outside of the washing machine.

Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the disclosure.

In accordance with one aspect of the present disclosure, a washing machine includes a main body, a tub vertically arranged within the main body, a passage case including a first drainage pipe connected to a lower portion of the tub and a branch pipe to allow wash water introduced from the first drainage pipe to be introduced into the tub again, a pump including a pump case having a first pump inlet arranged at a relatively higher position than the branch pipe and a motor coupled to one end of the pump case so as to supply power to pump the wash water introduced into the first pump inlet, and a bubble generating unit to generate bubbles in the wash water pumped by the pump.

The passage case may further include a second drainage pipe communicated with the first drainage pipe to guide the wash water to an outside of the washing machine.

The branch pipe may further include at least one foreign matter inflow preventing rib to filter out foreign matter contained in the wash water introduced from the first drainage pipe, and the foreign matter inflow preventing rib may protrude from an inner peripheral surface of the branch pipe.

The pump case may further include a second pump inlet connected to a lower end of the tub, and the second pump inlet may be arranged at a relatively higher position than the first pump inlet.

The pump case may be provided, at an upper portion thereof, with a foreign matter inflow preventing bump to filter out foreign matter contained in the wash water within the tub, and the second pump inlet may be formed at an inner side of the foreign matter inflow preventing bump.

The pump case may further include a foreign matter inflow preventing wall to filter out foreign matter contained in the wash water introduced from the first pump inlet.

The foreign matter inflow preventing wall may be provided at a central portion of the pump case, and the wash water introduced from the first pump inlet may be introduced into the foreign matter inflow preventing wall, and is then pumped to the bubble generating unit.

The pump case may include a motor coupling portion which is coupled with the motor to supply power to pump the wash water introduced from the first or second pump inlet, and a pump outlet to guide the wash water, which is pumped, to the bubble generating unit, and the pump outlet may be provided at an outer peripheral surface of the motor coupling portion to be communicated with the motor coupling portion.

The pump case may include a first receiving portion to receive the wash water introduced from the first or second pump inlet, and a second receiving portion connected, at one end thereof, with the first receiving portion while being connected, at the other end thereof, with the motor coupling portion, and the first and second receiving portions may be partitioned by the foreign matter inflow preventing wall.

The foreign matter inflow preventing wall may further include a residual water removal hole to remove the wash water which remains in the second receiving portion.

The bubble generating unit may include a first passage into which the wash water pumped by the pump is introduced, a second passage having a relatively smaller sectional area than the first passage, and an air inlet communicated with the second passage in order to supply air to the wash water flowing through the second passage.

The second drainage pipe may be provided with a valve so that the wash water introduced from the first drainage pipe flows toward either the second drainage pipe or the branch pipe.

The washing machine may further include a first connecting hose to connect the branch pipe and the first pump inlet, and a second connecting hose to connect the pump outlet and the bubble generating unit.

In accordance with another aspect of the present disclosure, a washing machine includes a main body, a tub vertically arranged within the main body, a passage case including a first drainage pipe communicated with the tub so that wash water in the tub is introduced into the first drainage pipe, a second drainage pipe to discharge the wash water introduced into the first drainage pipe to an outside of the washing machine, and a branch pipe to change a movement direction of the wash water introduced into the first drainage pipe while being arranged to be spaced apart from a bottom of the tub by a predetermined length, a pump including a pump case having a first pump passage arranged to be more adjacent to the tub than the branch pipe, and a motor connected to one side of the pump case so as to pump the wash water introduced through the first pump passage, and a bubble generating unit having an air inlet to supply air to the wash water pumped by the pump.

The pump case may further include a second pump passage, which is communicated with a lower end of the tub and is provided above the first pump passage.

The pump case may further include a foreign matter inflow preventing wall to filter out foreign matter contained in the wash water introduced through the first pump passage.

The foreign matter inflow preventing wall may be provided, at an outer peripheral surface, with a residual water removal hole so that the wash water, which remains at an inner side of the foreign matter inflow preventing wall, flows toward the second drainage pipe.

The branch pipe may further include at least one foreign matter inflow preventing rib protruding from an inner peripheral surface of the branch pipe so as to filter out foreign matter contained in the wash water.

The bubble generating unit may include a wash water passage through which the wash water pumped by the pump flows, and an air passage communicated with the wash water passage in order to supply air to the wash water flowing through the wash water passage.

In accordance with another aspect of the present disclosure, a method of controlling a washing machine which includes a main body, a tub vertically arranged within the main body, a drainage pipe communicated with the tub, a pump arranged at a lower portion of the tub, and a bubble generating unit to generate bubbles in wash water pumped by the pump, includes sensing a water level of the wash water during supply of the wash water into the tub, and determining whether drainage of the wash water supplied into the tub is needed, wherein when the water level of the wash water is increased at a level more than a predetermined height, the drainage pipe is closed so that the wash water is controlled to be transferred to the pump, and when the drainage of the wash water is determined to be needed, the drainage pipe is opened so that the wash water is controlled to be discharged outside the washing machine through the drainage pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a sectional view illustrating a washing machine according to an exemplary embodiment of the present disclosure;

FIG. 2 is a partially sectional view illustrating the tub, a passage case, a pump, and a bubble generating unit selected from FIG. 1;

FIG. 3 is a bottom view illustrating the tub of FIG. 1 as viewed from the bottom;

FIG. 4 is a partially sectional view illustrating the passage case selected from FIG. 2;

FIG. 5 is a partially sectional view illustrating the pump selected from FIG. 2;

FIG. 6 is a sectional view illustrating the bubble generating unit selected from FIG. 2;

FIG. 7 is a view illustrating the flow of the wash water when bubbles are generated in the wash water; and

FIG. 8 is a view illustrating the flow of the wash water when the wash water is discharged.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

FIG. 1 is a sectional view illustrating a washing machine according to an exemplary embodiment of the present disclosure.

As shown in FIG. 1, the washing machine, which is designated by reference numeral 1, includes a main body 10 to define an external appearance of the washing machine 1, a tub 20 arranged within the main body 10, a rotary tub 30 rotatably arranged within the tub 20, and a drive unit 40 arranged at a lower portion of the tub 20 to rotate the rotary tub 30.

The main body 10 is provided, at an upper portion thereof, with a cover 15 having a laundry input hole 14 so as to put laundry into the rotary tub 30. The cover 15 is provided with a door 16 to open and close the laundry input hole 14.

The tub 20 is respectively connected, at outer sides thereof, with suspension units 21 to allow the tub 20 to be suspended from and supported by the main body 10. The tub 20 is coupled, at an upper end thereof, with an annular tub cover 70 to cover the tub 20.

The rotary tub 30 is rotatably arranged within the tub 20, and has a number of through holes 31.

The rotary tub 30 is rotatably mounted, at a base thereof, with a pulsator 35. The pulsator 35 serves to agitate the laundry put into the rotary tub 30 together with wash water.

The drive unit 40 includes a clutch 41 to rotate the rotary tub 30 and the pulsator 35, and a drive motor 43 to drive the clutch 41. The drive motor 43 is connected to the clutch 41 by a pulley and a belt so as to transfer drive force to the rotary tub 30 and the pulsator 35.

The tub 20 is installed, at an upper portion thereof, with a water supply unit 50 to supply the wash water to the tub 20. The water supply unit 50 includes a water supply valve 53 to control supply of water, and a water supply pipe 51 to connect the water supply valve 53 and a washing agent supply unit 60.

The water supply pipe 51 is connected, at one side thereof, with an outside water supply source (not shown) while being connected, at the other side thereof, with the washing agent supply unit 60.

The washing agent supply unit 60 includes a case 61 provided within the cover 15, and a washing agent container 63 which is detachably mounted at the case 61 and stores each washing agent. The case 61 is formed, at a bottom thereof, with a discharge hole 65 to discharge the wash water in which the washing agents are dissolved.

Water to be supplied through the water supply pipe 51 is supplied into the tub 20 together with the washing agents via the washing agent supply unit 60.

FIG. 2 is a partially sectional view illustrating the tub, a passage case, a pump, and a bubble generating unit selected from FIG. 1. FIG. 3 is a bottom view illustrating the tub of FIG. 1 as viewed from the bottom. FIG. 4 is a partially sectional view illustrating the passage case selected from FIG. 2. FIG. 5 is a partially sectional view illustrating the pump selected from FIG. 2. FIG. 6 is a sectional view illustrating the bubble generating unit selected from FIG. 2.

As shown in FIGS. 2 to 6, the tub is coupled, at the lower portion thereof, with the passage case 120, the pump 150, and the bubble generating unit 180. The passage case 120 guides the wash water so that the wash water is discharged from the tub 20 to the outside of the washing machine 1 or is introduced into the tub 20 again. The pump 150 serves to pump the wash water passing through the passage case 120. The bubble generating unit 180 supplies air to the wash water pumped by the pump 150 so as to generate bubbles.

The passage case 120 includes a first drainage pipe 122 connected to the tub 20, a branch pipe 124 to guide the wash water introduced into the first drainage pipe 122 to the pump 150, and a second drainage pipe 126 to discharge the wash water introduced into the first drainage pipe 122 to the outside of the washing machine 1.

The first drainage pipe 122 is coupled to one end of a lower side of the tub 20 to be communicated with the tub 20 so that the wash water in the tub 20 may be introduced into the passage case 120.

The wash water introduced into the passage case 120 through the first drainage pipe 122 flows into the branch pipe 124 or the second drainage pipe 126 via a branch portion 128.

The branch pipe 124 changes a flow direction of the wash water introduced through the first drainage pipe 122 to guide the wash water toward the pump 150. The branch pipe 124 includes at least one foreign matter inflow preventing rib 132 to filter out foreign matter such as lint which may be contained in the wash water. The foreign matter inflow preventing ribs 132 protrude from an inner peripheral surface of the branch pipe 124 by a length corresponding to substantially one half of a diameter of the branch pipe 124, respectively while being arranged to be evenly spaced apart from and be in parallel with one another. Such a foreign matter inflow preventing rib 132 filters out the foreign matter such as lint, which may be contained in the wash water, without affecting the flow of the wash water passing through the branch pipe 124. Since each foreign matter inflow preventing rib 132 also protrudes from the inner peripheral surface of the upper side of the branch pipe 124 by a predetermined length, the foreign matter contained in the wash water, which is discharged during discharge of the wash water, may be freely discharged through the second drainage pipe 126 without being filtered out by the foreign matter inflow preventing rib 132.

The second drainage pipe 126 discharges the wash water introduced through the first drainage pipe 122 to the outside of the washing machine 1.

The second drainage pipe 126 is further provided with a valve 134. When the second drainage pipe 126 is opened during movement of the wash water in the tub 20, the wash water is discharged through the second drainage pipe 126 without flowing into the branch pipe 124. In addition, the valve 134 closes the second drainage pipe 126 during movement of the wash water, thereby preventing the wash water from being discharged through the second drainage pipe 126.

The pump 150 includes a pump case 152 to define a passage through which the wash water flows, and a motor 154 connected to one end of the pump case 152 so as to supply power to pump the wash water within the pump case 152.

The pump case 152 includes a first pump inlet 161 to introduce the wash water passing through the branch pipe 124, a second pump inlet 162 communicated with a lower end of the tub 20, a foreign matter inflow preventing wall 164 to filter out the foreign matter contained in the wash water which is introduced from the first pump inlet 161, first and second receiving portions 171 and 172 partitioned by the foreign matter inflow preventing wall 164, a motor coupling portion 174 to couple the pump case 152 and the motor 154, and a pump outlet 176 provided at an outer peripheral surface of the motor coupling portion 174.

The first pump inlet 161 guides the wash water so that the wash water passing through the branch pipe 124 may be introduced into the pump case 152, and is thus arranged at a relatively higher location than the branch pipe 124. Since the first pump inlet 161 is arranged at a higher position than the branch pipe 124, the wash water may be smoothly discharged outside the washing machine 1. Such a configuration will be described in detail below.

The second pump inlet 162 is provided at an upper portion of the pump case 152 so that the pump case 152 is communicated with a lower end of the tub 20, thereby directly introducing the wash water in the tub 20 into the pump case 152. The second pump inlet 162 is arranged at a higher position than the first pump inlet 161. During discharge of the wash water, the wash water being directly introduced into the pump case 152 through the second pump inlet 162 pressurizes wash water in the pump case 152 so that the wash water in the pump case 152 may smoothly flow toward the passage case 120 through the first pump inlet 161.

Meanwhile, in terms of the configuration in which the first and second pump inlets 161 and 162 define passages to introduce the wash water into the pump case 152, respectively, the first and second pump inlets 161 and 162 may be referred to as first and second pump passages 161 a and 162 a, respectively.

The foreign matter such as lint contained in the wash water, which is introduced into the pump case 152 through the second pump inlet 162, is filtered out by a foreign matter inflow preventing bump 163. The foreign matter inflow preventing bump 163 protrudes upwards inside the tub 20 from the upper portion of the pump case 152, and the second pump inlet 162 is formed at an inner side of the foreign matter inflow preventing bump 163.

The foreign matter inflow preventing wall 164 is provided at a substantially central portion of the pump case 152 while having a hollow cylindrical shape so as to prevent the foreign matter contained in the wash water, which is introduced from the first pump inlet 161, from being introduced toward an impeller (not shown) which is connected to the motor 154 and is rotated. As described above, the foreign matter contained in the wash water within the tub 20 is primarily filtered out by the foreign matter inflow preventing ribs 132 provided in the branch pipe 124, and then foreign matter, which is not filtered out by the foreign matter inflow preventing ribs 132, is secondarily filtered out by the foreign matter inflow preventing wall 164.

The first and second receiving portions 171 and 172 in the pump case 152 are partitioned from each other by the foreign matter inflow preventing wall 164.

The first receiving portion 171 is a space formed at an outer side of the foreign matter inflow preventing wall 164 while having a shape surrounding the second receiving portion 172. Accordingly, the first receiving portion 171 guides the wash water so that the wash water introduced from the first and second pump inlets 161 and 162 may be received in the first receiving portion 171, and then be introduced into the second receiving portion 172.

The second receiving portion 172 is a space formed at an inner side of the foreign matter inflow preventing wall 164 while being communicated, at one end thereof, with the first receiving portion 171 and being communicated, at the other end thereof, with the motor coupling portion 174. Accordingly, the second receiving portion 172 guides the wash water so that the wash water is introduced from the first receiving portion 171 into the motor coupling portion 174.

The foreign matter inflow preventing wall 164 is provided, at a lower portion thereof, with a residual water removal hole 173 which is communicated with the second receiving portion 172. The residual water removal hole 173 guides residual water, which may remain in the second receiving portion 172 after discharge of the wash water, to the first pump inlet 161 so that the residual water may be discharged through the second drainage pipe 126.

The motor coupling portion 174 is provided at one end of the pump case 152, and is coupled with the motor 154 which supplies power to pump the wash water introduced from the second receiving portion 172. The impeller (not shown) is coupled to a rotational shaft of the motor 154 and is rotated, in order to supply power to transfer the wash water introduced into the motor coupling portion 174 to the bubble generating unit 180.

The pump outlet 176 is provided at the outer peripheral surface of the motor coupling portion 174 to be communicated with the motor coupling portion 174 so as to guide the pumped wash water to the bubble generating unit 180.

The bubble generating unit 180 includes a wash water passage 184 which is a flow passage of the wash water, and an air inlet 190 to supply air to the wash water flowing through the wash water passage 184.

The wash water passage 184 includes first and second passages 181 and 182 while having a substantially circular shape in section and being formed to pass through an inner portion of the bubble generating unit 180.

The first passage 181 is formed to extend within the bubble generating unit 180 by a predetermined length. The second passage 182 is communicated with the first passage 181 while having a relatively smaller diameter D2 than the diameter D1 of the first passage 181. The second passage 182 is also formed to extend within the bubble generating unit 180 by a predetermined length.

A diameter reducing portion 183 is provided between the first and second passages 181 and 182 so as to reduce resistance undergone during movement of the wash water from the first passage 181 to the second passage 182.

The air inlet 190 is penetrated into the inner portion of the bubble generating unit 180 from an outer peripheral surface of the bubble generating unit 180 to be communicated with the second passage 182. The air inlet 190 may have a smaller diameter than the diameter D2 of the second passage 182, for the purpose of smooth flow of air. The air inlet 190 is coupled, at one end thereof, with an air inflow hose 192 which is coupled to the tub cover 70, as shown in FIG. 1, so that air in the tub cover 70 may be introduced into the air inlet 190.

When the wash water flowing through the first passage 181 is introduced into the second passage 182 having a smaller diameter than the first passage 181, the velocity of the wash water introduced into the second passage 182 is increased more than the wash water flowing through the first passage 181. As a result, the pressure in the second passage 182 is reduced in proportion to the increase in velocity.

In this case, a pressure difference between a section of the second passage 182 and the outside of the bubble generating unit 180 is generated in proportion to the reduction in pressure in the second passage 182. Consequently, the outside air of the bubble generating unit 180 is introduced into the second passage 182 through the air inlet 190 by the pressure difference, thereby being mixed with the wash water.

Such a phenomenon is referred to as the Venturi effect. In accordance with the Venturi effect, when fluid passes through passages having different diameters and sectional areas from each other, the velocity of the fluid is increased in proportion to the square of the diameter of the passage, whereas the pressure of the fluid is reduced in proportion to the increased velocity squared.

Due to the structure in which the inner portion the bubble generating unit 180 is formed with the passages having different diameters from the each other and is additionally formed with the air inlet 190, bubbles may be generated by supplying air to the wash water.

Since the bubble generating unit 180 is coupled, at one end thereof, to the lower end of the tub 20, and the second passage 182 is communicated with the lower end of the tub 20, the wash water passing through the second passage 182 is introduced into the tub 20 in a state containing the bubbles as described above.

The branch pipe 124 and the first pump inlet 161 may be connected by a first connecting hose 142, and the pump outlet 176 and the first passage 181 may be connected by a second connecting hose 144. The first and second connecting hoses 142 and 144 serve to prevent generation of leakage during the flow of the wash water. Since being made of a synthetic resin material such as synthetic rubber, the first and second connecting hoses 142 and 144 may stably transfer the wash water without being damage even when the first and second connecting hoses 142 and 144 strike the tub 20 by external impact or internal vibration.

Hereinafter, a process in which bubbles are generated in the wash water or the wash water is discharged will be described.

FIG. 7 is a view illustrating the flow of the wash water when bubbles are generated in the wash water. FIG. 8 is a view illustrating the flow of the wash water when the wash water is discharged.

As shown in FIG. 7, the wash water in the tub 20 is introduced into the passage case 120 through the first drainage pipe 122. In this case, the valve 134 mounted at the second drainage pipe 126 closes the second drainage pipe 126 so that the wash water introduced through the first drainage pipe 122 is not discharged through the second drainage pipe 126. The wash water introduced through the first drainage pipe 122 passes through the branch pipe 124 in a state in which foreign matter is primarily filtered out by the foreign matter inflow preventing ribs 132 provided at the branch pipe 124. Subsequently, the wash water is introduced into the pump case 152 through the first connecting hose 142 and the first pump inlet 161.

The wash water introduced into the pump case 152 passes through the first receiving portion 171 while being secondarily filtered out by the foreign matter inflow preventing wall 164, and is then introduced into the motor coupling portion 174 through the second receiving portion 172. Meanwhile, the wash water in the tub 20 may be directly introduced into the first receiving portion 171 of the pump case 152 through the second pump inlet 162 without passing through the passage case 120 to join the wash water introduced into the first receiving portion 171 via the passage case 120, and then be introduced into the motor coupling portion 174 through the second receiving portion 172. The wash water introduced into the motor coupling portion 174 is transferred to the bubble generating unit 180 via the pump outlet 176 by the impeller.

The wash water transferred to the bubble generating unit 180 is injected into the tub 20 again in the state containing bubbles while passing through the first and second passages 181 and 182.

As shown in FIG. 8, when the wash water is discharged outside the washing machine 1, the wash water in the tub 20 is discharged through the second drainage pipe 126 or through the second pump inlet 162. In this case, the valve 134 opens the second drainage pipe 126 so that the wash water passing through the first drainage pipe 122 may be discharged through the second drainage pipe 126.

The wash water being introduced through the second pump inlet 162 provided at the upper portion of the pump case 152 pressurizes wash water in the pump case 152 so that the wash water in the pump case 152 may flow toward the first pump inlet 161. Consequently, the wash water introduced into the first pump inlet 161 may smoothly flow toward the branch pipe 124 arranged at a relatively lower position than the first pump inlet 161 by gravity.

The wash water passing through the branch pipe 124 is discharged outside the washing machine 1 through the second drainage pipe 126.

Meanwhile, the residual water, which may remain in the second receiving portion 172 also after discharge of the wash water, may be discharged outside the washing machine 1 through the first pump inlet 161 and the second drainage pipe 126 by the residual water removal hole 173.

As is apparent from the above description, in accordance with the washing machine according to the exemplary embodiments of the present disclosure, improvement of washing performance may be achieved by generation of bubbles in the wash water introduced into the tub.

Furthermore, in accordance with the washing machine according to the exemplary embodiments of the present disclosure, the wash water may be rapidly discharged outside the washing machine.

Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. 

1. A washing machine comprising: a main body; a tub vertically arranged within the main body; a passage case comprising a first drainage pipe connected to a lower portion of the tub, and a branch pipe to allow wash water introduced from the first drainage pipe to be introduced into the tub again; a pump comprising a pump case having a first pump inlet arranged at a relatively higher position than the branch pipe, and a motor coupled to one end of the pump case so as to supply power to pump the wash water introduced into the first pump inlet; and a bubble generating unit to generate bubbles in the wash water pumped by the pump.
 2. The washing machine according to claim 1, wherein the passage case further comprises a second drainage pipe communicated with the first drainage pipe to guide the wash water to an outside of the washing machine.
 3. The washing machine according to claim 1, wherein: the branch pipe further comprises at least one foreign matter inflow preventing rib to filter out foreign matter contained in the wash water introduced from the first drainage pipe; and the foreign matter inflow preventing rib protrudes from an inner peripheral surface of the branch pipe.
 4. The washing machine according to claim 1, wherein: the pump case further comprises a second pump inlet connected to a lower end of the tub; and the second pump inlet is arranged at a relatively higher position than the first pump inlet.
 5. The washing machine according to claim 4, wherein: the pump case is provided, at an upper portion thereof, with a foreign matter inflow preventing bump to filter out foreign matter contained in the wash water within the tub; and the second pump inlet is formed at an inner side of the foreign matter inflow preventing bump.
 6. The washing machine according to claim 1, wherein the pump case further comprises a foreign matter inflow preventing wall to filter out foreign matter contained in the wash water introduced from the first pump inlet.
 7. The washing machine according to claim 6, wherein: the foreign matter inflow preventing wall is provided at a central portion of the pump case; and the wash water introduced from the first pump inlet is introduced into the foreign matter inflow preventing wall, and is then pumped to the bubble generating unit.
 8. The washing machine according to claim 4, wherein: the pump case comprises a motor coupling portion which is coupled with the motor to supply power to pump the wash water introduced from the first or second pump inlet, and a pump outlet to guide the wash water, which is pumped, to the bubble generating unit; and the pump outlet is provided at an outer peripheral surface of the motor coupling portion to be communicated with the motor coupling portion.
 9. The washing machine according to claim 8, wherein: the pump case comprises a first receiving portion to receive the wash water introduced from the first or second pump inlet, and a second receiving portion connected, at one end thereof, with the first receiving portion while being connected, at the other end thereof, with the motor coupling portion; and the first and second receiving portions are partitioned by the foreign matter inflow preventing wall.
 10. The washing machine according to claim 9, wherein the foreign matter inflow preventing wall further comprises a residual water removal hole to remove the wash water which remains in the second receiving portion.
 11. The washing machine according to claim 1, wherein the bubble generating unit comprises: a first passage into which the wash water pumped by the pump is introduced; a second passage having a relatively smaller sectional area than the first passage; and an air inlet communicated with the second passage in order to supply air to the wash water flowing through the second passage.
 12. The washing machine according to claim 2, wherein the second drainage pipe is provided with a valve so that the wash water introduced from the first drainage pipe flows toward either the second drainage pipe or the branch pipe.
 13. The washing machine according to claim 9, further comprising: a first connecting hose to connect the branch pipe and the first pump inlet; and a second connecting hose to connect the pump outlet and the bubble generating unit.
 14. A washing machine comprising: a main body; a tub vertically arranged within the main body; a passage case comprising a first drainage pipe communicated with the tub so that wash water in the tub is introduced into the first drainage pipe, a second drainage pipe to discharge the wash water introduced into the first drainage pipe to an outside of the washing machine, and a branch pipe to change a movement direction of the wash water introduced into the first drainage pipe while being arranged to be spaced apart from a bottom of the tub by a predetermined length; a pump comprising a pump case having a first pump passage arranged to be more adjacent to the tub than the branch pipe, and a motor connected to one side of the pump case so as to pump the wash water introduced through the first pump passage; and a bubble generating unit having an air inlet to supply air to the wash water pumped by the pump.
 15. The washing machine according to claim 14, wherein the pump case further comprises a second pump passage, which is communicated with a lower end of the tub and is provided above the first pump passage.
 16. The washing machine according to claim 14, wherein the pump case further comprises a foreign matter inflow preventing wall to filter out foreign matter contained in the wash water introduced through the first pump passage.
 17. The washing machine according to claim 16, wherein the foreign matter inflow preventing wall is provided, at an outer peripheral surface, with a residual water removal hole so that the wash water, which remains at an inner side of the foreign matter inflow preventing wall, flows toward the second drainage pipe.
 18. The washing machine according to claim 14, wherein the branch pipe further comprises at least one foreign matter inflow preventing rib protruding from an inner peripheral surface of the branch pipe so as to filter out foreign matter contained in the wash water.
 19. The washing machine according to claim 14, wherein the bubble generating unit comprises; a wash water passage through which the wash water pumped by the pump flows; and an air passage communicated with the wash water passage in order to supply air to the wash water flowing through the wash water passage.
 20. A method of controlling a washing machine which includes a main body, a tub vertically arranged within the main body, a drainage pipe communicated with the tub, a pump arranged at a lower portion of the tub, and a bubble generating unit to generate bubbles in wash water pumped by the pump, the method comprising: sensing a water level of the wash water during supply of the wash water into the tub; and determining whether drainage of the wash water supplied into the tub is needed, wherein when the water level of the wash water is increased at a level more than a predetermined height, the drainage pipe is closed so that the wash water is controlled to be transferred to the pump, and when the drainage of the wash water is determined to be needed, the drainage pipe is opened so that the wash water is controlled to be discharged outside the washing machine through the drainage pipe. 